I would like to know that am I subjected to disciplinary action if I asked my superior on how he can become manager? Example : "How you become a manager?" I was accused of challenging this person and my fault was labeled as insubordination. Please help me.

I agree with VKPC on this - it depends on your tone and in what context. So it depends on what the the tribunal/judge perceived when presented with the overall story. Words can amount to threat and/or assault as well, depending on the context on how it is and in what situation it is said.